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Photoionised gas pressure enlarges molecular cloud shells by 17 percent at 10 Myr while cloud structure decides expansion or re-collapse.

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T0 review · grok-4.3

2026-06-29 15:25 UTC pith:NYCOXME3

load-bearing objection TRINITY adds a phase-aware pressure rule to thin-shell modeling and runs a useful parameter survey, but the 17% radius enlargement rests on that modeling choice. the 1 major comments →

arxiv 2605.27517 v1 pith:NYCOXME3 submitted 2026-05-26 astro-ph.GA astro-ph.IM

TRINITY: A coupled model of winds, radiation, and photoionised gas in molecular clouds. I. Methods and validation

Jia Wei Teh , Ralf S. Klessen , Simon C. O. Glover , Kathryn Kreckel This is my paper
classification astro-ph.GA astro-ph.IM
keywords molecular cloudsstellar feedbackphotoionisationH II regionscloud dispersalthin-shell modelwindsradiation pressure
verification ladder T0 review T1 audit T2 compute T3 formal T4 reserved

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper presents TRINITY, a 1D thin-shell code that follows how stellar winds, radiation pressure, photoionised gas pressure, and gravity act together on a cloud shell. It demonstrates that photoionised gas pressure remains dynamically important even after the energy-driven phase ends and that the initial cloud density profile controls whether the shell re-collapses or keeps expanding. These results address the observed 1-5 Myr cloud dispersal times seen in multi-wavelength surveys, which occur before the first supernovae. The code tests a range of cloud masses, core densities, and star-formation efficiencies to show how different feedback components couple to the shell.

Core claim

TRINITY evolves the bubble-shell structure under winds, supernovae, direct and dust-reprocessed radiation pressure, P_HII, and gravity. A phase-aware prescription drives the shell with the larger of the hot-bubble and photoionised pressures when energy-driven, and P_HII plus ram pressure when momentum-driven. Validation against analytic limits shows that P_HII enlarges the shell radius by roughly 17 percent at 10 Myr in the fiducial run. At higher efficiency the energy-driven phase lasts under 1 Myr, radiation pressure stays sub-dominant, and P_HII remains dynamically important in the momentum-driven phase. Cloud structure sets both phase durations and outcomes: at fixed mass, core density,

What carries the argument

TRINITY, the 1D thin-shell code that uses a phase-aware pressure prescription to drive the shell.

Load-bearing premise

The phase-aware prescription that drives the shell with the larger of the hot-bubble and photoionised pressures when energy-driven and with P_HII plus ram pressure when momentum-driven.

What would settle it

A measurement of shell radii in clouds with known density profiles that shows whether the 17 percent enlargement at 10 Myr due to photoionised pressure is present or absent.

Watch this falsifier — get emailed when new claim-graph text bears on it.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit.

Referee Report

1 major / 1 minor

Summary. The manuscript introduces TRINITY, a 1D thin-shell code that evolves the bubble-shell structure in molecular clouds under the combined effects of stellar winds, supernovae, direct and dust-reprocessed radiation pressure, photoionised-gas pressure (P_HII), and gravity. It extends WARPFIELD by incorporating a phase-aware pressure prescription, multiple initial cloud density profiles (uniform, piecewise power-law, Bonnor-Ebert), evolving shell structure, cooling, and LyC escape. The code is validated against analytic wind and photoionisation limits and applied to a parameter survey spanning cloud masses 10^5-10^6.5 M_⊙, core densities 10^3-10^4 cm^{-3}, and star-formation efficiencies ε=0.01-0.30. Key results are that P_HII enlarges the shell radius by ~17% at 10 Myr in the fiducial run, the energy-driven phase shortens at higher ε, radiation pressure remains sub-dominant, P_HII stays important in the momentum-driven phase, and cloud structure controls phase durations and dispersal outcomes.

Significance. If the central modeling choices are robust, TRINITY supplies an efficient, interpretable framework for mapping feedback dominance across cloud parameter space. Strengths include explicit validation against analytic limits, a reproducible parameter survey showing consistent trends, and the demonstration that both P_HII and initial cloud structure shape expansion even at fixed stellar population. These elements would make the work a useful tool for interpreting multi-wavelength observations of cloud dispersal on 1-5 Myr timescales.

major comments (1)
  1. [Abstract] Abstract (and the methods description of the phase-aware prescription): the quantitative claim that P_HII enlarges the shell radius by roughly 17% at 10 Myr, together with statements on phase durations and P_HII dominance in the momentum-driven regime, is produced by the specific rule that drives the shell with the larger of hot-bubble and photoionised pressures when energy-driven and with P_HII plus ram pressure when momentum-driven. This rule is introduced as a modeling choice rather than derived from the thin-shell equations or validated against resolved hydrodynamics; the 17% figure therefore inherits any systematic bias introduced at the energy-to-momentum transition.
minor comments (1)
  1. [Abstract] The abstract states that TRINITY 'succeeds WARPFIELD' but does not specify which numerical or physical improvements are new versus inherited; a short explicit comparison table or paragraph would clarify the advance.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful review and for identifying the need to clarify the justification of the phase-aware pressure prescription. We address the major comment below.

read point-by-point responses

  1. Referee: [Abstract] Abstract (and the methods description of the phase-aware prescription): the quantitative claim that P_HII enlarges the shell radius by roughly 17% at 10 Myr, together with statements on phase durations and P_HII dominance in the momentum-driven regime, is produced by the specific rule that drives the shell with the larger of hot-bubble and photoionised pressures when energy-driven and with P_HII plus ram pressure when momentum-driven. This rule is introduced as a modeling choice rather than derived from the thin-shell equations or validated against resolved hydrodynamics; the 17% figure therefore inherits any systematic bias introduced at the energy-to-momentum transition.

    Authors: We agree that the phase-aware rule is a modeling choice rather than a direct derivation from the thin-shell equations. It is motivated by the physical expectation that, in the energy-driven phase, the shell responds to the larger of the two internal pressures, while in the momentum-driven phase the photoionised gas supplies the dominant driving term together with ram pressure. The overall model is validated against analytic wind-bubble and Strömgren-sphere limits, but we acknowledge that the transition itself is not tested against resolved hydrodynamics. We will revise the methods and abstract sections to state this approximation explicitly, to qualify the 17% figure as arising within this framework, and to note that full hydrodynamical validation of the transition remains desirable. These changes will be incorporated in the revised manuscript. revision: yes

Circularity Check

0 steps flagged

No significant circularity; model uses explicit prescriptions validated externally

full rationale

The paper introduces TRINITY as a 1D thin-shell numerical code implementing explicit phase-aware pressure rules as modeling choices, validated against analytic wind and photoionisation limits. Quantitative outputs such as the 17% radius enlargement at 10 Myr are produced by forward integration of the model equations rather than by fitting parameters to the target quantities or by self-referential definitions. No load-bearing step reduces by construction to its own inputs, and the derivation chain remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

Model rests on standard 1D thin-shell hydrodynamics and feedback coupling assumptions; no new entities introduced and parameters are surveyed rather than fitted to match a target result.

free parameters (1)
  • star-formation efficiency ε
    Input parameter surveyed from 0.01-0.30; not fitted to reproduce a specific observable in the central claim.
axioms (2)
  • domain assumption Thin-shell approximation for bubble-shell structure
    Code evolves 1D thin-shell structure under multiple pressures and gravity.
  • domain assumption Phase-aware pressure driving rule
    Shell driven by larger of hot-bubble and photoionised pressures in energy-driven phase.

pith-pipeline@v0.9.1-grok · 5968 in / 1425 out tokens · 47108 ms · 2026-06-29T15:25:33.299254+00:00 · methodology

0 comments
read the original abstract

Multi-wavelength surveys place cloud dispersal at 1-5 Myr after massive stars emerge, before the first supernovae. Whether a cloud disperses, re-collapses, or leaks Lyman-continuum (LyC) photons depends on how pre-supernova winds, radiation pressure, and photoionised-gas pressure ($P_{\rm HII}$) couple to the shell. We introduce TRINITY, a 1D thin-shell code that succeeds WARPFIELD. TRINITY evolves the bubble-shell structure under winds, supernovae, direct and dust-reprocessed radiation pressure, $P_{\rm HII}$, and gravity. A phase-aware prescription drives the shell with the larger of the hot-bubble and photoionised pressures when energy-driven, and $P_{\rm HII}$ plus ram pressure when momentum-driven. The initial cloud may be uniform, a piecewise power law, or a Bonnor-Ebert sphere; shell structure, hot-bubble cooling, photon absorption, and LyC escape evolve with the dynamics. We validate against analytic wind and photoionisation limits and survey clouds of mass $10^5$-$10^{6.5}\,M_\odot$, core density $10^3$-$10^4$ cm$^{-3}$, and star-formation efficiency $\varepsilon=0.01$-$0.30$. $P_{\rm HII}$ enlarges the shell radius by roughly 17% at 10 Myr in the fiducial run. At higher efficiency, the energy-driven phase lasts under 1 Myr, radiation pressure stays sub-dominant, and $P_{\rm HII}$ remains dynamically important in the momentum-driven phase. Cloud structure sets both phase durations and outcomes: at fixed mass, core density, and efficiency, homogeneous and shallow clouds re-collapse while a steep $\rho\propto r^{-2}$ cloud keeps expanding, and Bonnor-Ebert clouds disperse roughly 55% later than homogeneous ones. Thus $P_{\rm HII}$ and cloud structure both shape feedback-driven expansion even when the stellar population is fixed. TRINITY is an efficient, interpretable framework to map feedback dominance across cloud parameter space and resolved H II regions.

Figures

Figures reproduced from arXiv: 2605.27517 by Jia Wei Teh, Kathryn Kreckel, Ralf S. Klessen, Simon C. O. Glover.

Figure 1
Figure 1. Figure 1: Schematic of the bubble geometry and evolutionary sequence modelled by Trinity. The central cluster (yellow stars) injects free-streaming winds (light blue), which thermalise at the wind termination shock Rts. The shocked wind fills the hot bubble out to the bubble radius Rb (red). Outside Rb, the swept-up shell contains an ionised layer (pink) bounded by the ionisation-front radius Rif, and a neutral laye… view at source ↗
Figure 2
Figure 2. Figure 2: Bubble radius evolution for the fiducial test cloud (Mcloud = 106 M⊙, ncore = 103 cm−3 , ε = 0.01), comparing Trinity (full physics) with a warpfield-equivalent run ob￾tained by turning PHII off, and with three analytic limiting solutions in a uniform medium without gravity: the energy￾driven Weaver wind, the photoionised Spitzer expansion, and the momentum-driven snowplow. For this run, the inclusion of P… view at source ↗
Figure 3
Figure 3. Figure 3: Diagnostic outputs of Trinity for a run with Mcloud = 106 M⊙, ncore = 103 cm−3 , and ε = 0.10. Top: bubble ra￾dius Rb(t), reverse-shock radius Rts(t), shell radius Rsh(t), and bubble velocity vb(t), with the energy-driven, transition, and momentum-driven phases marked. Middle: fractional force bud￾get on the shell, normalised to the sum of force magnitudes. The outer stack shows gravity Fgrav, the total dr… view at source ↗
Figure 4
Figure 4. Figure 4: Top: density profiles (solid, left axis) and enclosed mass (dashed, right axis) for the four configurations in Sect. 4.2. All share ncore = 104 cm−3 , Mcloud = 105 M⊙ and ε = 0.01; steeper slopes concentrate mass toward the core, reducing the mass en￾countered by the expanding shell at large radii. Bottom: bubble radius Rb(t). The bubble within a αρ = −2 profile accelerates into the declining density gradi… view at source ↗
Figure 5
Figure 5. Figure 5: Phase timeline for the four density profiles in Sect. 2.5. Each horizontal bar shows the duration of the energy-driven (white), transition (light grey), momentum-driven (hatched), and re-collapse (dark grey) phases. At fixed Mcloud, ncore, Rcore, and ε, changing only the density profile shifts both the phase du￾rations and the final outcome. Only the αρ = −2 cloud avoids re-collapse within the 4 Myr runtim… view at source ↗
Figure 6
Figure 6. Figure 6: Dispersal timescale τdisp as a function of cluster stel￾lar mass M⋆ at fixed central density ncore = 103 cm−3 . Top: Bonnor–Ebert profile. Bottom: homogeneous profile. Marker colour encodes the star-formation efficiency ε ∈ [0.01, 0.3]; marker size scales with Mcloud from 105 to 106.5 M⊙. At fixed (Mcloud, ε), the Bonnor–Ebert clouds disperse ∼ 55% later than the homogeneous clouds. This systematic offset … view at source ↗

discussion (0)

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Reference graph

Works this paper leans on

3 extracted references · 1 canonical work pages · 1 internal anchor

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    Adamo, A., Bradley, L. D., Vanzella, E., et al. 2024, Nature, 632, 513 Alves, J. F., Lada, C. J., & Lada, E. A. 2001, Nature, 409, 159 8 https://github.com/JiaWeiTeh/simplify Article number, page 14 of 22 J. W. Teh et al.: Trinity I: Unified feedback in bubbles Arthur, S. J., Medina, S.-N. X., & Henney, W. J. 2016, MNRAS, 463, 2864 Baes, M., Verstappen, J...

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    We do not model pre-main-sequence (PMS) evolu- tion

    supplies the feedback tables from that moment on- ward. We do not model pre-main-sequence (PMS) evolu- tion. The error this introduces depends on two things: how long PMS contraction takes for a star of given mass, and which mass range actually generates the feedback. We ad- dress them in turn. To answer the first, we use the MESA Isochrones and Stellar T...

    2016

  3. [3]

    The third samples the cumulative arc length, sk = kX j=1 q (˜rj − ˜rj−1)2 + (˜yj − ˜yj−1)2, (E.2) at Nmin equally spaced positions along the curve

    The second detector flags local extrema from sign changes in the derivative. The third samples the cumulative arc length, sk = kX j=1 q (˜rj − ˜rj−1)2 + (˜yj − ˜yj−1)2, (E.2) at Nmin equally spaced positions along the curve. The initial kept set is the union of these three detector outputs and the two endpoints of the original array. A subset of the kept ...

    2026